Cutting tool



Feb. 8, 1944-. BETT|N| 2,341,309

CUTTING TOOL Filed oct. 28, 1940 Patented Feb. 8, 1944 UNITED STATESPATENT OFFICE CUTTING TOOL I David Joseph Bettini, Baltimore, Md.,assignor' to Locke Insulator Corporation, Baltimore, Md., a corporationof Maryland Application October 28, 1940, Serial No. 363,222

2 claims.

The invention relates to insulators and more particularly to a tool forremoving from insulator bushings that portion of the clay which tends tocause cracks and hence renders the bushing unfit for electrical use.

The principal object of the invention, generally considered, is toprovide a cutting tool which may be inserted in the opening of thebushing and rotated therein, such cutting tool being adapted to cleanlycut a conical section from the bushing without detriment to the interioror exterior thereof.

Another object of the invention is to provide a cutting tool which isextremely simple in construction and in which the angle of the conicalsection to be cut may be regulated and which, by the substitution ofsimple parts, may be used with bushings of various sizes.

A still further object of the invention is to provide a cutting toolwhich may be rotated about its axis of symmetry and in which the cuttingelements are taut wires which will cut clay without any tendency to dragthe portions of the clay through which the wire is adapted to pass.

To these and other ends the invention comprises the various elements ashereinafter set forth, the novel features thereof being pointed out inthe appended claims.

In the drawing:

Figure 1 is a side elevational view of the cutting tool in operativeposition in a bushing blank.

Figure 2 is a sectional view on the line 2-2 of Figure 1, the directionof view being indicated by the arrows adjacent said section line.

Figures 3 and 4 are, respectively, side elevations of bushing blanksshowing in dotted lines the openings therein and also indicated bydotted lines are the conical sections removed by rotation of the cuttingtool.

Figures 5 and 6 are respectively partial sections on lines 55 and 65 ofFigures 3 and 4.

Figure 7 is an enlarged view of the end of the cutting tool showing themethod of maintaining the cutting wires in position.

Before describing the invention in detail it might be pointed out thatin the manufacture of bushings it has been common practice to provide inthe orifice of the pug mill a die member centrally disposed withreference to the surrounding walls of the orifice and by which alongitudinally extending opening of the desired configuration and sizemay be forced in the clay as extruded. Definite lengths of the extrudedpug are cut as the clay is being extruded and these pug segments arethen allowed to dry until they reacheither the leather or the bone drystate. In the leather dry state they may be operated upon by a profilemachine and the necessary ribs, skirts or corrugations formed on theirexterior surfaces, or if the clay is allowed to reach the bone dry statethe necessary surface conformation can be produced by the use of propergrinding wheels and tools. It has been known fora great number of yearsthat, in bushing blanks in which the diameter of the bushing is largecompared with the diameter of the orifice, during the drying stage avery large percentage will develop incipient cracks adjacent the centralopening. These cracks, of course, destroy the value of the bushing as anelectrical insulator. In a number of casesthe cracks do not developuntil after the insulator has been glazed and fired, the result being agreat decrease in volume production and a tremendous factory loss due todefects in the insulator not appearing until after the entire cycle ofoperation thereon has been performed.

- Attempts have been made to obviate the formation of these cracks byinserting in the ends of the bushing blank opening properly shapedwooden plugs so as to compress the clay by enlarging the ends of. theopening in the bushing, but such attempts have been found detrimentalrather than beneficial.

As a-result of the investigation carried on by the applicant he hasdetermined that the cracks above described are primarily due to the factthat the clay in the central portion of the insulator has beencompressed to a high degree by its passage over an adjacent die member,the cutting of the pug permitting the clay adjacent the ends of the cutpug to expand to relieve the compression strains, and such expansion ofthe clay forms incipient cracks which are nearly microscopic indimension in the initial stage but which, on the drying of the insulatorblank tend to increase both in size and depth. Applicant found furtherthat by removing from the ends of each pug or preliminary insulatorblank a conical section from the clay surrounding the central openingthere is no tendency of the clay to expand adjacent the thus enlargedopening. To accomplish this clay removal simply and expeditiouslywithout injury to the surrounding body applicant has devised the toolillustrated in the accompanying drawing and which will now be describedin detail.

In the drawing the cutting tool comprises a handle I to which is rigidlyconnected a metal rod 2 having at the outer end thereof a slot or frombushings having openings of different diameters. f v I I Adjustablymounted on the rod between the cap and the handle I is a cylindricaldisk 6 having a boss 1 provided with an opening 8 in which a set screw 9is positioned and by means of which the disk 6 may be adjustablypositioned on the rod 2 at any desired point. The' disk isprovided withrecesses H) at or adjacent the pe-/ riphery into which are received andsecured the ends of a wire II, the latter preferably beingseated withinthe slot 3 formed in the outer end of the rod 2.

It will be understood that by substituting disks of different diametersthe angle which the wires l l form with reference to the longitudinalaxis of the rod 2 can be adjusted so that the maximum diameter of theconical section to be cut from the interior ofthe bushing can beadjusted as desired. Such adjustment may also be made by merelyextending the recesses H1 in the form of radial slots in the disk andsecuring the Wires at any desired position in such slots.

The operation of the device is as follows:

After the insulator blank has been brought to the leather dry state theoperator grasps the handle of the cutting tool and forces the end of thesame into the opening l2 of the bushing, and after the rod has movedinto the opening a predetermined distance, which may be indicated forexample by the marks I3 carried by the rod I2, the handle is rotated,causing the wires H to cut from the bushing a conical segment of theshape designated by the reference character I4. The cutting tool is thenremoved, causing the conical segments to be withdrawn from the openingand the operation is repeated at the opposite end of the bushing,forming at'each end of the bushing a frusto-conical opening of thedesired size and depth, both of which may be regulated with great nicetyby the instrument hereinbefore described. Not only is the bushing thusprevented from cracking but the enlarged opening in each end thereofcauses a much more rapid and even drying of the bushing and in thismanner tend materially to reduce the formation of incipient or visiblecracks in the bushing blank.

It is common practice to provide the openings in the bushing ofcruci-form shape, indicated by the reference character [5, but it willbe obvious to those skilled in the art that by the use of the cap 5,whose external diameter is equal to the diameter of the cylindricalsegments of the cruciform opening, conical segments may be removed frombushings of this type by the same tool operated in exactly the samemanner.

It will be apparent to those skilled in the art that a single wire maybe used rather than a pair of wires and that the tool so modified wouldoperate in the same manner and perform the same operation.

Having thus described my invention, what I claim is:

1. A rotatable tool for forming a frusto-conical opening in a clay'mass,comprising a rod having at one end a cylindrical thimble concentric withthe longitudinal axis of said rod, said thimble engaging the inner wallof an opening in said clay mass to position said tool and center thesame during the rotation thereof, a member slidably positioned on saidrod and extending normal to the longitudinal axis thereof, a pair ofwires extending from diametrically opposite points on the surface ofsaid rod to said slidable member, said wires each making a predeterminedangle with the longitudinal axis of said rod, and means for rotatingsaid rod about its longitudinal axis.

2. A-rotatable tool for forming a frusto-conical opening in a clay mass,comprising a rod having at one end a. cylindrical thimble concentricwith the longitudinal axis of said rod, said thimble engaging the innerwall of an opening in said clay mass to position said tool and centerthe same during the rotation thereof, a disk member slidably positionedon said rod and concentric therewith, and a pair of cutting membersextending from diametrically opposite points on the surface of said rodand adjacent the inner end of said thimble and connected todiametrically opposite points on said disk member, said last namedpoints being equally spaced from the longitudinal axis of said rod, andmeans for rotating said rod about its longitudinal axis.

DAVID JOSEPH BETTINI.

